Method of grinding in tube-mills.



M. J. DAVIDSEN.

METHOD OF GRINDING IN TUBE MILLS.

APPLICATIOII FIHED AUGJ. m3.

LI IIEWID Patented 1m. 14, 1915.

lll

MEYER, JQSEPH D1957 IDSEN, (BF-PARKS, llilltAlfl'CE.

METHOD '5 GRINDING IN TUBE-MILES.

Specification of Letters Patent.

Peltehted Dec. let,

Implication filed August "1', 193.3. Serial No. 733,??0.

To all whom it may concern:

Be it known that l, MEYER J osnrrr DAVID- snnya subject of the King'of Denmark, residing in Paris, France, have invented certain new, and useful Improvements in Methods of, Grinding in Tube- Mills, of

which the following is a specification, reference being had to, the accompanying drawing, which forms a pert hereof.

This invention relates to the fine grinding of various substances, such as cement clinker, coal for use in rotary kilns, etc., in drums rotating on horizontal axes which are -charged with relatively small grinding bodies such as flint pebbles or metallic grinding bodies, which are free within the drums and have motion only in vertical planes at right angles to the axis of rotation. The ob-- ject of the invention is to increase the sillciency of such grinding mills, that is, to increase the output per horse power required to drive the mills. D

In accordance with the present invention the charge of grinding bodies is reduced to about one-half, by weight per cubic foot, of the charge which has been employed heretofore, the weight of the material being ground and in the drum at any one time is also preferably reduced somewhet as compared with ordinary practice. say to about ten per cent. of the Weight of the grinding bodies, and. the speed of rotation. of the drum is considerably increased, so that the grind-- ing bodies fall through a greater or less distance within the drum and the rolling and rubbing action of the grinding bodies which is characteristic of the oldpractice is re placed by 'a heating or hammering action under the new practice, which is found to be much more effective in pulverizing' the material in the drum.

The intention will. be understood more readily by reference to the accompanying drawing which illustrates the action of grinding bodies under the present i nveu tion.

The drum 0;, which the grind is curried on, may be of any suitable threensmus,

they would be quickly broken up by the hammering action it is preferable to use metallic grinding bodies in the practice of the new method.

The volume o'f metallic grinding bodies employed in the new method is much smaller than the volume of flint pebbles employed in the old method, but'it will be understood that in the new method there is employed about half the quantity by weight of grind ing bodies of the same kind that is employed in the practice of the old method, although the proportions may differ more or less. The quantity of material being ground which is permitted to be in the drum et any one time is preferably somewhat less under the new method than under the old method, being preferably about ten per cent. of the weight of the grinding bodies. No attempt is made to represent in the drawing the me,- terial being ground.

In the practice of the new method, with a considerably lighter charge of grinding bodies, the drum is driven at a considerablyhigher rate of speed than under the old method. The speed of rotation is not pre cisely limited, but in general, it may be stated as approximately equal, in revolutions per minute, to the quotient of 45 divided. by the square root of the diameter expressed in meters. The speed may be expressed in the formula as follows:

in which D is the diameter of the drum. in meters. The speed of rotation of the drum under tl'ie new method not determined arbitrarily but is dependent upon certain known factors. a The speed at which the muss will begin to he carried around with t drum that at which the centrifugal force l'x-zconie est that the resultauts of the centrilug'al rce and the force of gravity which act upon any particle of the mass fall wholly outside the circumference of the drum, so that a pa ticle. "or example. at the zenith point of it path is acted on. by a, centrifu orce which )oth equul and opposite to force K j, "thereby the particle carried l. the zenith point without relative motion d ends on the other side of the zenith ut Contact with the shell of the drum. ed at which the particles of" the males to more enribicnl speeds i; at the HAC GQSGd Lil-3 centrifugal force is 1135 ier c ntum boe 'UJHL Weight of the combined. mess of grinding bodies an material. It niigliiz be expected that if the centrifugal -force e ceecis i-he force of gravity the entire charge of grinding bodies and material would he carried around with the drum. Because of minor factors which have not )eeii taken into account, particularly ihe slipping of the grinding bodies and material-0n the shell or lining of the drum, this is not the case, but at this point, when Elie reizfiive Weighi; ofthe charge is reduced as before described, the grinding bodies and material are carried. to a point near the zenith and considerably above the point Where the components cease to receive mechanical support from the components below them. As they approach the Zenith point the components of the mass leave the shell of the drum and, under the influence of their own momentum as well as of the force of gravity and the centrifugal force more in no 111001115 toward the opposite and lower side of the drum so that their action is changed from the rolling and rubbing action under the old moth V i in e heating or hammering; action which much more efiective in pulverizing the ierial.

It is found in pres/nice that with film in crease in speed and. the decrease in weight of the charge of grinding bodies. the horse power required to drive a grinding mill r i .1 m M- gr'otcr snpp the combined hi5 material and necessary, in Wet I is s im;

io ntion in order to sol-w:-

the results 1.. ram forth. it; will also lw understood. that although pziriicnlnr refer-- ence has been iiml herein to ilio preferred weight of grinding bodies per cubic {eon ii. is necesserv that. the hull: oi ilH' (,(miliinwi of idli g bodies and ill llL' lill l not he so grin: i 5.0 "'nrnish iivchufx; porn; for the grincln bodies to n \Jlr? c they may he sari-Mi lmroinl n11 zvnii ii in contiici \riih lie shell.

I claim as my invention The method of grinding: mnlwrinl {liar consists in producing by centrifugal force only a przieQ llv coniinuous. thin whirling! layer of coinl: 5 an! ;3;rin lin;z bodies about Morin [till axis in :in twin terrnpled endiesspnlh and 211' surli :l sjiwil :is co both SillJSiAdl'Clfliij conll; 'l: ili' ltiifl and bodies to s permit a forwa i and material to 1" the same.

This specification si ml and \riinuwml this 25th day oi July, ,1 Op, WEI).

Signed in the presence 01 portm: o1

point 

